OnBoardAntennaInterSatellitesPhaseModifier.java
/* Copyright 2002-2022 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.estimation.measurements.modifiers;
import java.util.Collections;
import java.util.List;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.gnss.InterSatellitesPhase;
import org.orekit.frames.Transform;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedPVCoordinates;
/** On-board antenna offset effect on inter-satellites phase measurements.
* @author Bryan Cazabonne
* @since 10.3
*/
public class OnBoardAntennaInterSatellitesPhaseModifier implements EstimationModifier<InterSatellitesPhase> {
/** Position of the Antenna Phase Center in satellite 1 frame. */
private final Vector3D antennaPhaseCenter1;
/** Position of the Antenna Phase Center in satellite 2 frame. */
private final Vector3D antennaPhaseCenter2;
/** Simple constructor.
* @param antennaPhaseCenter1 position of the Antenna Phase Center in satellite 1 frame
* (i.e. the satellite which receives the signal and performs the measurement)
* @param antennaPhaseCenter2 position of the Antenna Phase Center in satellite 2 frame
* (i.e. the satellite which simply emits the signal in the one-way
* case, or reflects the signal in the two-way case)
*/
public OnBoardAntennaInterSatellitesPhaseModifier(final Vector3D antennaPhaseCenter1,
final Vector3D antennaPhaseCenter2) {
this.antennaPhaseCenter1 = antennaPhaseCenter1;
this.antennaPhaseCenter2 = antennaPhaseCenter2;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
@Override
public void modify(final EstimatedMeasurement<InterSatellitesPhase> estimated) {
// The participants are satellite 2 at emission, satellite 1 at reception
final TimeStampedPVCoordinates[] participants = estimated.getParticipants();
final AbsoluteDate emissionDate = participants[0].getDate();
final AbsoluteDate receptionDate = participants[1].getDate();
// transforms from spacecraft to inertial frame at emission/reception dates
final SpacecraftState localState = estimated.getStates()[0];
final SpacecraftState receptionState = localState.shiftedBy(receptionDate.durationFrom(localState.getDate()));
final Transform receptionSpacecraftToInert = receptionState.toTransform().getInverse();
final SpacecraftState remoteState = estimated.getStates()[1];
final SpacecraftState emissionState = remoteState.shiftedBy(emissionDate.durationFrom(remoteState.getDate()));
final Transform emissionSpacecraftToInert = emissionState.toTransform().getInverse();
// Compute the geometrical value of the inter-satellites range directly from participants positions.
final Vector3D pSpacecraftReception = receptionSpacecraftToInert.transformPosition(Vector3D.ZERO);
final Vector3D pSpacecraftEmission = emissionSpacecraftToInert.transformPosition(Vector3D.ZERO);
final double interSatellitesRangeUsingSpacecraftCenter = Vector3D.distance(pSpacecraftEmission, pSpacecraftReception);
// Compute the geometrical value of the range replacing
// The spacecraft positions with antenna phase center positions
final Vector3D pAPCReception = receptionSpacecraftToInert.transformPosition(antennaPhaseCenter1);
final Vector3D pAPCEmission = emissionSpacecraftToInert.transformPosition(antennaPhaseCenter2);
final double interSatellitesRangeUsingAntennaPhaseCenter = Vector3D.distance(pAPCEmission, pAPCReception);
// Get the estimated value before this modifier is applied
final double[] value = estimated.getEstimatedValue();
// Modify the phase value by applying measurement wavelength
final double wavelength = estimated.getObservedMeasurement().getWavelength();
value[0] += (interSatellitesRangeUsingAntennaPhaseCenter - interSatellitesRangeUsingSpacecraftCenter) / wavelength;
estimated.setEstimatedValue(value);
}
}